Abstract:
This paper reports on measurements of the thermal conductivity $\varkappa$ and the electrical resistivity $\rho$ in the temperature range 5–300 K, and, at 300 K, on X-ray diffraction studies of high-porosity (with a channel pore volume fraction of $\sim$47 vol%) of the beech wood biocarbon prepared by pyrolysis (carbonization) of tree wood in an argon flow at the carbonization temperature $T_{\mathrm{carb}}$ = 800$^\circ$C. It has been shown that the biocarbon template of the samples studied represents essentially a nanocomposite made up of amorphous carbon and nanocrystallites –“graphite fragments” and graphene layers. The sizes of the nanocrystallites forming these nanocomposites have been determined. The dependences $\rho(T)$ and $\varkappa(T)$ have been measured for the samples cut along and perpendicular to the tree growth direction, thus permitting determination of the magnitude of the anisotropy of these parameters. The dependences $\rho(T)$ and $\varkappa(T)$, which have been obtained for beech biocarbon samples prepared at $T_{\mathrm{carb}}$ = 800$^\circ$C, are compared with the data amassed by us earlier for samples fabricated at $T_{\mathrm{carb}}$ = 1000 and 2400$^\circ$C. The magnitude and temperature dependence of the phonon thermal conductivity of the nanocomposite making up the beech biocarbon template at $T_{\mathrm{carb}}$ = 800$^\circ$C have been found.
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